Concept: Pathogenic bacteria often possess external virulence factors to evade the host immune system.

Solution: The capsule is a tightly bound, thick, sticky outer layer of polysaccharides surrounding the cell wall of many bacteria. It is famously known for hiding the bacteria from host macrophages (preventing phagocytosis) and facilitating adherence for biofilms.

Distractor Autopsy: Slime layers are similar but much looser and easily washed off. Spores are dormant internal structures for survival, not external coverings.